Polyamide graft copolymers

ABSTRACT

Amino acid functionalized polymers useful for graft copolymerization prepared by reacting a mixture containing, for chain transfer, a thio-substituted amino acid and an ethylenically unsaturated monomer.

BACKGROUND OF THE INVENTION

[0001] Research leading to the conception and reduction to practice ofthe invention was supported in part by Grant No. DE 09307-08 issued bythe National Institutes of Health (NIH). The United States Governmenthas certain rights in and to the claimed invention.

FIELD OF THE INVENTION

[0002] The present invention relates to novel amino acid functionalizedmacrormonomers or polymer precursors, methods for their preparation andnovel methods for preparing novel graft copolymers therewith.

DESCRIPTION OF THE PRIOR ART

[0003] It is often desirable to combine two or more polymer systems toobtain a product which exhibits the properties of each system. Mostpolymers, however, are mutually incompatible in that they cannot beintimately admixed or blended to produce a product having a homogeneouscomposition.

[0004] One solution is to graft copolymerize two or more polymer systemssuch that the product contains segments of each component homogeneouslydistributed throughout the copolymer, each contributing its desirableproperties thereto.

[0005] Although physical blends or mixtures of, e.g., polymers A and Bmay be incompatible, a graft copolymer of A with another polymer (C)compatible with polymer (B) will enable the production of a homogenousblend of A/C and B. Graft copolymers with segments of dissimilarchemistries have been shown to be useful in a variety of applications assurfactants, compatibilizers, impact modifiers and surface modifiers.

[0006] Although it is possible to graft a polymer onto a previouslypolymerized backbone, these procedures are typically “messy”, oftenrequiring radiation or an energy source to promote grafting. It isusually very difficult to ensure the production of a homogeneous graftcopolymer since this type of grafting usually results in a cross-linkedbase material, as well as a cross-linked layer of grafted polymer.

[0007] Most conventional routes to graft copolymers involve employing anintermediate “macromonomer” which is a polymer/oligomer with afunctional group capable of undergoing further chemical reactionpolymerization. Macromonomers are most often obtained by anionicpolymerization. The conditions attendant anionic polymerization,however, severely limit the number and nature of monomers which can bepolymerized thereby. Moreover, a majority of the studies thus far havefocussed on the synthesis of macromonomers capable of reacting withvinyl monomers to form graft copolymers.

[0008] There are few reports of well defined polyamide graft copolymerswith addition polymers such as poly(acrylates) or poly(methacrylates).Most attempts of amide graft copolymerizations with addition polymersinvolve either the in situ formation of graft copolymers in polymerblends or radiation induced surface graft techniques. Although effectivefor their intended applications, neither method produces a well definedgraft copolymer.

[0009] It is an object of the present invention to utilize novelfree-radical chain transfer methods to create novel macromonomers whichare capable of undergoing novel condensation polymerization reactionswith polymers to prepare novel graft copolymers.

[0010] Another object of the invention is to provide condensationpolymerizable macromonomers, more specifically, amino acid terminatedmacromonomers, and a novel route to the synthesis of polyamide graftcopolymers.

SUMMARY OF THE INVENTION

[0011] The above and other objects are realized by the presentinvention, one embodiment of which relates to a method of preparing anamino acid functionalized macromonomer composition having a degree ofpolymerization of from about 5 to about 20,000 comprising reacting byfree radical polymerization a mixture comprising:

[0012] (a) for chain transfer an amino acid having the formula:

[0013] wherein:

[0014] R₁ and R₂ are H or lower alkyl, e.g., CH₃; and

[0015] Z is alkylene, e.g., ethylene, propylene, butylene and the like;arylene, e.g., phenyl, biphenyl; and

[0016] (b) at least one polymerizable ethylenically unsaturated monomer,e.g., acrylates, e.g., alkyl acrylate, phenyl acrylate, cycloaliphaticacrylate; methacrylates, e.g., alkyl methacrylate, phenyl methacrylate,cycloaliphatic methacrylate; fluoro-substituted acrylates, e.g.,octafluoropentyl methacrylate; fluoro-substituted alkenes such asethene, propene, butene, butadiene, hexene and octene, such that, as aresult of reacting said mixture, at least 10 mol percent of themacromonomer composition product has the end group:

[0017] A further embodiment of the invention comprises a macromonomerprepared according to the above-described method.

[0018] Another embodiment of the invention is an amino acidfunctionalized addition-polymerized macromonomer composition having adegree of polymerization of from about 5.0 to about 20,000.

[0019] An additional embodiment of the invention relates to a method ofpreparing a graft copolymer of a polyamide comprising reacting undercondensation polymerization conditions a mixture comprising:

[0020] (a) a macromonomer described above, and

[0021] (b) a monomeric mixture which forms a polyamide by condensationpolymerization.

[0022] Other embodiments of the invention comprise a graft copolymerprepared by the above-described method, as well as graft copolymers of apolyamide and the above-described macromonomer composition.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1-3, 5 and 7 are schematic representations of reactionschemes of various of the methods of the invention.

[0024]FIG. 4 is a graphic representation of a Mayo plot of amacromonomer of the invention.

[0025]FIG. 6 is a graphic representation of a transmission FTIR of anacrylate-amide copolymer.

[0026]FIG. 8 is a tabular representation of the composition of a graftcopolymer of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] The present invention is predicated on the utilization ofmercaptans or —SH substituted compounds as chain transfer, molecularweight reducing agents to prepare macromonomers suitable for graftcopolymerization with a wide variety of polymers via condensationpolymerization routes. The chain transfer mechanism is set forth inFIG. 1. If the mercaptan is functionalized, the resulting polymer issimilarly functionalized as depicted in reactions 5 and 6 of FIG. 1.

[0028] It is preferred to employ thiol- or mercaptan-terminated aminoacids as chain transfer agents. An amino acid functionality is preferredover other end groups such as diacids or diamines due to the inherentstoichiometry that it provides. This stoichiometry is required in thecondensation graft reaction to ensure the highest degree ofpolymerization possible.

[0029] Generally, the method of the invention involves the free radicalpolymerization of ethylenically unsaturated monomers in the presence ofthe functional chain transfer agent. Mercaptans, compounds containing asulfur-hydrogen bond, are commonly used in chain transfer reactions. Infact, mercaptans are commonly used to control molecular weight incommercial polymerization reactors [Ito, Macromolecules, Vol. 10, page821 (1977); Rosen, Fundamental Principles of Polymeric Materials, pages103-128, Wiley & Sons, New York (1982)]. Cysteine, a naturally occurringamino acid, contains the sulf-hydryl group required for mercaptan chaintransfer reactions. The addition of cysteine, an effective chaintransfer agent, results in amino acid functionality.

[0030] It will be understood, however, by those skilled in the art thatany thiol- or mercapto-substituted amino acid capable of functioning asa chain transfer agent may be employed in the practice of the invention.

[0031] Exemplary of such amino acids are those embraced by the abovestructural formula, e.g., cysteine.

[0032] The macromonomers may be derived from any suitableaddition-polymerizable ethylenically unsaturated monomer such as, e.g.,methyl acrylate, methyl methacrylate, tert-butylacrylate, cyclohexylacrylate, cyclohexyl methacrylate, butyl acrylate, butyl methacrylate,phenyl acrylate and phenyl methacrylate.

[0033] The reaction of macromonomer formation can be modeled by the MayoEquation: $\begin{matrix}{\frac{1}{{DP}_{n}} = {\frac{1}{{DP}_{no}} + {C_{S}\frac{\lbrack S\rbrack}{\lbrack M\rbrack}}}} & \lbrack 2.1\rbrack\end{matrix}$

[0034] wherein:

[0035] C_(s)=chain transfer constant

[0036] [S]=chain transfer agent concentration

[0037] [M]=monomer concentration

[0038] DP_(n)=degree of polymerization

[0039] DP_(no)=degree of polymerization without chain transfer agent.

[0040] The equation enables a determination of the efficiency of thechain transfer for functionalizing growing polymer chains.

[0041] The degree of polymerization in the absence of chain transfer totransfer agent, DP_(no), can be described by equation 2.2:$\begin{matrix}{\frac{1}{{\overset{\_}{DP}}_{no}} = \frac{k_{1}\quad R_{p}}{{k_{p}^{2}\quad\lbrack M\rbrack}^{2}}} & \lbrack 2.2\rbrack\end{matrix}$

[0042] Substituting this value in equation 2.1 gives the Mayo equation(2.3) for prediction of the chain transfer constant: $\begin{matrix}{\frac{1}{{\overset{\_}{DP}}_{n}} = {\frac{1}{{\overset{\_}{DP}}_{no}} + {C_{S}\frac{\lbrack S\rbrack}{\lbrack M\rbrack}}}} & \lbrack 2.3\rbrack\end{matrix}$

[0043] This equation is valid only when the initiator concentration islow. By synthesizing a series of polymers with different ratios of chaintransfer agent to monomer, a Mayo plot can be used to determine theC_(s). Knowledge of the C_(s) for a particular system enables one toadjust the reactant concentrations in order to target a specific molarmass polymer.

[0044] The Mayo model can also be used to predict the functionality ofthe polymer obtained. If both sides of equation 2.3 are multiplied byDP_(n):$1 = {\frac{{\overset{\_}{DP}}_{n}}{{\overset{\_}{DP}}_{no}} + {{DP}_{n}C_{S}\frac{\lbrack S\rbrack}{\lbrack M\rbrack}}}$

[0045] where the two terms on the right represent the fraction ofunfunctionalized chains. If the value of C_(s) and, therefore, the rateof chain transfer is high, termination occurs primarily by chaintransfer and high rates of functionalization are expected. The extent offunctionalization also increases with increasing mercaptan content. If alower concentration of chain transfer agent is used or if a lower valueof C_(s) is observed, the probability of termination through othermethods such as disproportionation or combination increases. As othertermination mechanisms become more prevalent, the extent offunctionalization decreases.

[0046] It is important to note the limitations of the Mayo model. Thismodel is valid only under certain assumptions, one of which is thatchain transfer occurs exclusively to the chain transfer agent. Inpractice, however, some chain transfer to solvent and initiator isgenerally observed. Also, these values, as in the case of copolymerreactivity ratios, are valid at instantaneous conditions. In otherwords, low conversions are desired in order to limit the compositiondrift between the monomer and chain transfer agent. With theseassumptions in mind, determined values of C_(s) and predictedfunctionalities are only estimates or theoretical predictions assumingideal conditions. However, the model is valuable for making fairlyaccurate estimates provided these limitations are taken into account.

[0047] Most macromonomers synthesized to date using chain transferinvolve the preparation of vinyl terminated polymer chains. These freeradically polymerized macromonomers can be reacted with vinyl monomersto form graft copolymers. The technique has thus been largely limited toaddition-addition type chemistries. The present invention enables anexpansion of this technique to addition-condensation combinationsutilizing, e.g., polyamides and the condensation polymerizable backbone.Thus, polyamides could be surface modified or rubber-toughened by graftcopolymerization with a suitably functionalized macromonomer.

[0048] Initial attempts did not yield highly functionalized free radicalpolymerized chains. The molecular weight of the product was thus muchhigher than would be expected of a suitable macromonomer. It wassuspected that a side reaction may inhibit complete chain transfer.Further investigation revealed that the reaction depicted in FIG. 3 wascompeting with the chain transfer mechanism. Cysteine is ionizable tothe sulfur anion, the equilibrium reaction having a pKa of 8.3. Theanionic form reacts with, e.g., acrylates, to form the by-productS-carbobutoxyethyl cysteine. This side reaction reduces theconcentration of cysteine, resulting in an incomplete chain transfer.

[0049] By reducing the pH of the reaction to a value below the pKa ofthe chain transfer (i.e., about 8.3), the side reaction is substantiallyeliminated, thus greatly improving chain transfer. The pH should,therefore, be adjusted to a value greater than 0.0 and below about 8.0,preferably to a value between about 0.5 and about 3.5.

[0050] The mechanism by which functionalization can occur is depicted inFIG. 1. Steps 1 and 2 are typical processes of free radical initiation.When exposed to heat, the azobisisobutyronitrile (AIBN) breaks down intofree radicals and nitrogen gas is evolved. The AIBN radicals can thusinitiate the polymerization of vinyl compounds. If there is no chaintransfer agent present, the polymerization continues until terminationby disproportionation or combination occurs. In the presence of amercaptan, termination can occur through chain transfer.

[0051] The hydrogen from the sulfhydryl group of the mercaptan isreadily extractable. A propagating polymer chain can thus react with themercaptan (Step 3), terminating propagation and leaving a sulfur radicalon the mercaptan. If the concentration of mercaptan is high, themercaptan itself can react with the AIBN radical (Step 4), also giving asulfur radical. The resulting sulfur radical can then initiate the freeradical polymerization of a vinyl monomer (Step 5).

[0052] If the mercaptan contains hydroxyl or carboxylic acid functionalgroups (R′), the initiating sulfur radical introduces functionality toone end of the macromolecule. The growing functionalized polymer radicalcan again react with the mercaptan (Step 6), yielding a terminatedfunctionalized chain and another molecule of sulfur radical which canreact with more monomer (Step 5) to form a reaction loop. Theeffectiveness of functionalization is dependent on the chain transferconstant of the mercaptan, as well as the relative concentrations ofmercaptan, monomer and free radical initiator. The AIBN concentration iskept extremely low relative to the chain transfer agent to minimize thenumber of chains initiated by the AIBN. Any chains initiated by AIBNwill be non-functionalized (see Steps 2 and 3).

[0053] The advantage of this chain transfer method is that it can beused with a wide variety of vinyl monomer systems. Macromonomerscomposed of any monomer which can be polymerized free radically shouldbe able to be synthesized using this method. Also, macromonomers whichthemselves are random copolymers also become feasible.

[0054] The invention will be illustrated utilizing the amino acidcysteine; however, it will be understood by those skilled in the artthat any amino acid having the formula set forth above may be utilized,e.g., those wherein Z is an alkylene group having up to as many as 1,000carbon atoms or arylene, including those interrupted by an O atom, i.e.,ether groups. It is usually necessary that the thiol group and the aminogroup occupy carbon atoms separated from each other by at least onecarbon atom; i.e., that the thiol group occupy a carbon atom at least βto the carbon atom occupied by the amino group.

[0055]FIG. 2 sets forth a reaction scheme for the amino acidfunctionalization of butyl acrylate to form an amino acid terminatedpoly(butyl acrylate). Cysteine is a naturally occurring amino acidcontaining a reactive SH group. The mechanism depicted in FIG. 2 can beutilized to free radically polymerize a wide variety of monomers, bothhydrophobic and hydrophilic. Suitable such monomers include, e.g., butylacrylate, methyl acrylate, methyl methacrylate, tert-butyl acrylate,cyclohexyl acrylate, cyclohexyl methacrylate, butyl methacrylate, phenylacrylate, phenyl methacrylate and the like. Those skilled in the artwill realize that any free radically polymerizable monomer may bepolymerized according to the method of the invention to produce afunctionalized macromonomer.

[0056] As noted above, macromonomers and graft copolymers describedheretofore have been mostly limited to addition-addition copolymers.There are only a few cases in which addition-type macromonomers havebeen graft copolymerized with condensation-type monomers [Yamashita etal, Polym. Bull., Vol. 5, page 361 (1981); Chujo et al, Polym. Bull.,Vol. 8, page 239 (1982); Chujo et al, Polym. Comm., Vol. 25, page 278(1984); Chujo et al J. Polym. Sci., Polym. Chem. ed., Vol. 26, page 2991(1988)]. In order for the macromonomers to be capable of undergoingcondensation reactions in the production of graft copolymers, they mustbe difunctional. This does not mean that each end of the polymer must befunctionalized; it is only necessary and preferred that one end of thecopolymer contain a difunctional reactive group.

[0057] Only two authors have reported the synthesis of difunctionalmacromonomers using chain transfer agents. In Euro. Polym. J., Vol. 28,page 1527 (1992), Nair demonstrated the free radical chain transferpolymerization of styrene and various acrylates in the presence ofmercaptosuccinic acid. Dicarboxylic acid terminated polymers weresynthesized in a range of molecular weights from 1 to 10 kg/mol and wereshown to be highly functionalized.

[0058] Yamashita et al, supra, and Chujo et al, supra, carried out briefstudies on the preparation of dicarboxylic acid, as well as dihydroxylfunctional macromonomers of various methacrylate monomers. They alsoemployed mercaptosuccinic acid, as well as thioglycerol in themacromonomer preparation.

[0059] By applying the Mayo equation to a series of polymerizations withvarying chain transfer agent concentrations (see FIG. 4), the chaintransfer constant can be determined. The chain transfer constant forcysteine in the system of the invention is about 1.49 which is as highor higher than most of the mercaptans used in the synthesis of vinylfunctionalized macromonomers.

[0060] Inductively coupled plasma was employed to determine the sulfurconcentration and, therefore, the percent functionalization of themacromonomer described above. The results in Table 1 show thatincreasing the concentration chain transfer agent results in increasedfunctionality. TABLE 1 Functionalization of Butyl Acrylate OligomersWith Cysteine % Functionalization [S/M] × 10² Mn (Kg/mol) (ICP-Sconcentration) 0 63  0 1.6 5.9 72 3.2 2.6 75 6.4 1.2 84

[0061] The functionalized macromonomers of the invention may be employedin the novel method of the invention to form graft copolymers with awide variety of polymers such as, e.g., polyamides, i.e., nylons such asnylon 6, nylon 6,6, nylon 6,10, nylon 10 and nylon 12.

[0062] Generally, the graft copolymer is prepared by reacting undercondensation polymerization conditions a mixture comprising:

[0063] (a) for chain transfer, a macromonomer of claim 5 or 6, and

[0064] (b) a monomeric mixture which forms a polyamide by condensationpolymerization. More specifically, the monomeric mixture comprises:

[0065] (i) a mixture of a dicarboxylic acid having 1 to 10 carbon atomsand terminal carboxyl groups and a diamine having 1 to 12 carbon atomsand primary amino groups, salts, esters, amides and acid halides of thedicarboxylic acid and salts of the diamine;

[0066] (ii) amino monocarboxylic acids having 1 to 10 carbon atoms andprimary amino groups and terminal carboxyl groups, and

[0067] (iii) lactams, esters and amides of the amino carboxylic acids ormixtures of any of the above.

[0068] Specific examples include p-aminobenzoic acid and a mixture of1,6-phenylene diamine and adipic acid.

[0069] A reaction scheme for graft copolymerizing cysteinefunctionalized poly(butyl acrylate) and p-aminobenzoic acid to form apolyamide is depicted in FIG. 5. The transmission FTIR (FIG. 6) of theresulting product shows that a poly(butyl acrylate)-polyamide graftcopolymer is synthesized by this method.

[0070] The methods of the invention may be employed to design a varietyof condensation graft copolymers not heretofore available havingproperties not previously possessed by such systems. For example, theuse of low surface energy fluorinated macromonomers will enable theproduction of polyamides having modified surface properties, i.e., lowerthe moisture adsorption capability thereof. Employing rubberymacromonomers will result in impact toughened polyamides.

[0071] It will be understood by those skilled in the art having beenexposed to the description herein of the method of the invention thatthe latter is applicable to the formation of any functionalizedmacromonomer capable of entering into a condensation-type graftcopolymerization reaction.

[0072] The invention is illustrated by the following non-limitingexamples:

EXAMPLE 1

[0073] This example depicts the preparation of specific macromonomersutilizing cysteine as the chain transfer agent and butyl acrylate,methyl methacrylate and octafluoropentyl methacrylate as monomers.Azobisisobutyronitrile (AIBN) was used as the initiator.

[0074] Poly(butyl acrylate) was chosen because it has a very low glasstransition temperature (−54° C.) and, therefore, any graft copolymerscontaining it may be used as rubber modifiers. The fluoroacrylatecopolymer was chosen because, due to the low surface energy offluoropolymers in general, graft copolymers could be utilized as surfacemodifiers.

[0075] Synthetic procedure. Monomer concentrations in thepolymerizations were maintained constant at 16 wt. %. AIBNconcentrations also remained constant at 0.1 mol % of the monomerconcentration. Cysteine levels were varied in order to determine theireffect on the polymerization of acrylates and methacrylates.

[0076] In a typical polymerization, cysteine was dissolved in theprescribed amount of 10 N HCl in a 200 ml roundbottom flask equippedwith a magnetic stirrer. Water and tetrahydrofuran (THF) were then addedin concentrations yielding a 50 g solution of 96.5/3/0.5 ratio, byweight, THF/water/HCl. Ten grams of monomer were added and the desiredAIBN concentration was then dissolved in the reaction mixture. A refluxcondenser was attached to the flask. The reaction set-up was then placedin a glycerin bath at 65° C. and run for 6 hours under constantstirring. The isolation and purification of the various macromonomerssynthesized are described below.

[0077] A common solvent for both the monomer, either butyl acrylate orthe fluoroacrylate-MMA mixture, and the cysteine chain transfer agentmust be identified in order to ensure a homogeneous solution duringpolymerization. Cysteine is a crystalline powder insoluble in commonorganic solvents. Solubility tests in the approximate concentrationsrequired for synthesis of a 3 kg/mol macromonomer were performed. Asshown in Table 2, at the appropriate concentrations, cysteine isinsoluble in some common organic solvents which are suitable for thepolymerization of butyl acrylate. Furthermore, butyl acrylate iscompletely immiscible with water, quickly separating into two layers.TABLE 2 Solvent Determination for Monomer and Chain Transfer AgentToluene THF DMF Ethanol n-Butanol H₂O Cysteine i i i i i s Butylacrylate s s s s s i

[0078] Because of the strong H-bonding interactions within the aminoacid, it appeared necessary to add H₂O to disrupt crystalline structure.Cysteine was then pre-dissolved in water at high concentrations prior tothe addition of THF. This method was successful in keeping cysteinedissolved in a THF/water mixture. One of two things generally occurredupon the addition of butyl acrylate. Either the concentration of waterwas too high to allow the butyl acrylate to dissolve, or theconcentration was too low to prevent the precipitation of cysteine uponthe addition of the acrylate monomer. It was then determined thatethanol could be added in low concentrations in order to stabilize theTHF/water/cysteine/butyl acrylate solution. The ethanol was effective inpreventing the butyl acrylate from forming a second phase. Thecomposition of the solvent system used was an 80/10/10 ratio, by weight,of THF/EtOH/H₂O. The monomer concentration was 15 wt. %.

[0079] The synthesis of poly(butyl acrylate) in the presence of cysteinewas carried out using the solvent system described above. FIG. 2 depictsthe desired amino acid functionality of the macromonomer. Themonomer:cysteine:AIBN molar ratio used was 1000:30:1. The AIBNconcentration must be kept low in order to minimize the number of chainsinitiated by AIBN. As stated previously, any chains initiated by theAIBN initiator and not the chain transfer agent will be, in effect,“dead” chains. That is, they will lack the desired amino acidfunctionality. The polymerization was run under nitrogen at 65° C. for 7hours. A control polymerization was also run under the identicalconditions in the absence of the cysteine chain transfer agent. Theresulting polymers were isolated by rotary evaporation under vacuum at40° C. Due to its low glass transition temperature, poly(butyl acrylate)is virtually impossible to isolate by precipitation in a non-solvent.The reaction product of the control reaction was a clear, extremelytacky, viscous material with a yellowish haze. The cysteine modifiedproduct was very similar with the exception of the presence of a whiteprecipitate dispersed within the poly(butyl acrylate). This precipitatecould be separated from the polymer by dissolving the poly(butylacrylate) in THF. The precipitate was insoluble in THF and could,therefore, be collected by filtration.

[0080] The Mayo plot for butyl acrylate is set forth in FIG. 4.

[0081] As noted above, the side reaction depicted in FIG. 3 is reducedby carrying out the reaction at a reduced pH, i.e., below about 8.0 andabove 0.

EXAMPLE 2

[0082] The polyamide graft copolymer synthesis was carried out in asolvent system originally developed by Higashi et al [J. Polym. Sci.,Polym. Chem. ed., Vol. 18, pages 1711, 1841, 2875 (1980)] for thesolution polymerization of high molar mass polyamides. Thispolymerization of diacids and diamines was run in an NMP-pyridineso-solvent mixture, in the presence of triphenyl phosphite (TPP) andLiCl. The pyridine aids in the dissolution of the amino acid reactants.Triphenyl phosphite catalyzes the polymerization by reacting with theacids and amines to remove water from the condensation. LiCl facilitatesthe reaction of the triphenyl phosphite.

[0083] The condensation mechanism, as proposed by Higashi, isillustrated in FIGS. 5 and 7. Triphenyl phosphite reacts with LiCl toform a triphenyl phosphonium salt (FIG. 1, Step 1). The phosphonium saltthen reacts with a carboxylic acid to form a diphenyl phosphonium cationand a phenolic anion (Step 2). An amine can then attack the carboxylicacid, producing an amide linkage, diphenyl phosphite and phenol (Step3).

[0084] Synthesis. The synthesized graft copolymer compositions are shownin FIG. 8. Two different polyamide compositions, a wholly aromaticpoly(aminobenzoic acid) (PABA) and an aromatic-aliphatic poly(phenylenediamine-co-adipic acid) (PhDAA), were homopolymerized and graftcopolymerized in varying ratios with a 2.6 kg/mol amino acid-terminatedpoly(butyl acrylate) macromonomer. A control reaction was run in which a3.2 kg/mol unfunctionalized poly(butyl acrylate) was substituted for thelow molar mass poly(butyl acrylate) macromonomer. This unfunctionalizedp(BA) was synthesized using a butyl mercaptan chain transfer agent,which should result in an unreactive butyl end group. PhDAA was alsopolymerized in the presence of a 19.9 kg/mol poly(MMA-co-OFPMA)macromonomer.

[0085] In a typical reaction, 1.37 g of 2.6 kg/mol p(BA) macromonomer(0.53 mmol), 0.241 g (2.24 mmol) p-phenylenediamine, 0.326 g (2.24 mmol)adipic acid, 1.55 TPP (5 mmol) and 0.09 g LiCl were dissolved in 30 mlof an 80/20 NMP/pyridine solution and heated at 100° C. for 4 hours. Theresulting polymer, a tacky light brown solid, was obtained almostquantitatively by precipitation in an excess of 50/50 water/methanolnon-solvent, filtered, washed with methanol and dried overnight undervacuum at 40° C. The molar concentration of amide precursors andcatalysts were kept constant for all polymerizations.

[0086] The PABA-containing polyamides were insoluble in all commonorganic solvents. Those tried included THF, DMF, dichloroacetic acid andtrifluoroacetic acid. The only solvent found for both the PABAhomopolymer and copolymer was concentrated sulfuric acid. This is notsurprising given the similarity of the aromatic structure in PABA toKevlar®) polyamides. PhDAA homopolymer and copolymers were soluble inboth dichloroacetic acid and concentrated sulfuric acid.

[0087] All polyamide homopolymers and graft copolymers were Soxhletextracted with HPLC grade THF, a solvent for any unreacted acrylate ormethacrylate macromonomer.

[0088] The compositions of the purified graft copolymers were determinedby elemental analysis (EA) from the nitrogen content. Composition wasalso determined from the ¹H-NMR spectra of the graft copolymers usingthe integral ratios of aromatic protons from the polyamide to —CH₃protons from the poly(acrylate).

[0089] The measured graft copolymer chemical compositions are tabulatedin Table 3. The values calculated using NMR are in good agreement withthose from EA. Poly(butyl acrylate) content varies from 19 to 54 wt. %for the graft copolymer series. As expected, the poly(butyl acrylate)content in the graft copolymer increases with increasing feedconcentration.

[0090] The ratio of poly(acrylate) concentration in the copolymer to theinitial feed concentration was calculated and is also shown in Table 3.This ratio can be seen as a measure of % poly(acrylate) incorporation.Transmission FTIR spectra of the above-described system are shown inFIG. 6. TABLE 3 Chemical Composition of Purified Graft Copolymers fromElemental Analysis and NMR Graft Copolymer Graft CopolymerComposition^(EA) Composition^(NMR) Nitrogen (wt. %)* (wt. %)[Acrylate]_(copolymer**) Sample ID (wt. %)^(EA) Amide Acrylate AmideAcrylate [Acrylate]_(feed) 66PABA-g-33Bax 9.47 81 19 79 21 0.6133PABA-g-66Bax 6.35 54 46 60 40 0.65 33PhDAA-g-66Bax 7.03 55 45 54 460.69 10PhDAA-g-90Bax 6.42 46 54 47 53 0.60 33PhDAA-g-66Fax 9.64 75 25 7525 0.38

I claim:
 1. A method of preparing an amino acid functionalizedmacromonomer composition having a degree of polymerization of from about5 to about 20,000 comprising reacting by free radical polymerization amixture comprising: (a) for chain transfer, an amino acid having theformula:

wherein: R₁ and R₂ are H or CH₃; and Z is alkylene or arylene; and (b)at least one polymerizable ethylenically unsaturated monomer, such that,as a result of reacting said mixture, at least 10 mol percent of themacromonomer composition product has the end group:


2. A method of claim 1 wherein said amino acid is cysteine.
 3. A methodof claim 1 wherein said ethylenically unsaturated monomer is anacrylate.
 4. A method of claim 1 wherein said ethylenically unsaturatedmonomer is butyl acrylate, methyl acrylate, methyl methacrylate,tert-butyl-acrylate, cyclohexyl acrylate, cyclohexyl methacrylate, butylmethacrylate, phenyl acrylate or phenyl methacrylate.
 5. A macromonomerprepared by the method of claim
 1. 6. An amino acid functionalizedaddition-polymerized macromonomer composition having a degree ofpolymerization of from about 5 to about 20,000.
 7. The macromonomercomposition of claim 6 wherein said amino acid is cysteine.
 8. Themacromonomer composition of claim 6 wherein said addition-polymerizedmonomer is an acrylate.
 9. The macromonomer composition of claim 8wherein said acrylate is butyl acrylate.
 10. A method of preparing agraft copolymer of a polyamide comprising reacting under condensationpolymerization conditions a mixture comprising: (a) for chain transfer,a macromonomer of claim 5 or 6, and (b) a monomeric mixture which formsa polyamide by condensation polymerization.
 11. A method of claim 10wherein said monomeric mixture comprises: (i) a mixture of adicarboxylic acid having 1 to 10 carbon atoms and terminal carboxylgroups and a diamine having 1 to 12 carbon atoms and primary aminogroups, salts, esters, amides and acid halides of said dicarboxylic acidand salts of said diamine; (ii) amino monocarboxylic acids having 1 to10 carbon atoms and primary amino groups and terminal carboxyl groups,and (iii) lactams, esters and amides of said amino carboxylic acids. 12.A method of claim 11 wherein said monomeric mixture comprisesp-aminobenzoic acid.
 13. A graft copolymer prepared by the method ofclaim
 10. 14. A graft copolymer of a polyamide and a macromonomercomposition of claim 5 or 6.